Dual carriage impact printer with belt drive

ABSTRACT

An impact printing device in which two carriages are provided with complementary printing elements that are disposed on either side of the recording medium, such as paper. Each carriage is operatively connected to an elongated drive member and is movable thereby in the length direction of said drive members, while the paper moves in increments at right angles thereto. The carriages are arranged to be immovable with respect to each other and the driving means are belts having coupling elements that compensate for variations in belt lengths.

United States Patent Ljungberg Dec. 16, 1975 [54] DUAL CARRIAGE IMPACTPRINTER WITH 3,256,969 6/1966 Bretti 197/49 BELT DRIVE 3,565,230 2/1971Webberly et al. 197/49 3,795,299 3/1974 Nakamura et a1. 197/49 [75]Inventor: John Erik Ljungberg, Solna,

Sweden Primary ExaminerAnton O. Oechsle [73] Assignee: Facit Aktiebolag,Atvidaberg, Attorney, Agent, Firm-Alfred Miller Sweden 22 Filed: Dec.19, 1974 [57] ABSTRACT An impact printing device in which two carriagesare [21] APPI N05 534,363 provided with complementary printing elementsthat are disposed on either side of the recording medium, 52 U.S. c1197/1 R; 74/231 J; 101/9316; Such as paper. Each carriage is Operativelyconnected 197 97 to an elongated drive member and is movable thereby 51Int. (:1. B41J 19/00 in the length direction of Said drive members,While 58 Field of Search 197/1 R, 16, 49, 82-, the Paper moves inincrements at right angles thereto- 101/9315 93 1 93 7 93 The carriagesare arranged to be immovable with respect to each other and the drivingmeans are belts 5 References Cited having coupling elements thatcompensate for variations in belt lengths.

5 Claims, 3 Drawing Figures US. Patent Dec. 16, 1975 Sheet 1 of23,926,293

US. Patent Dec. 16,1975 Sheet2of2 3,926,293

DUAL CARRIAGE IMPACT PRINTER WITH BELT DRIVE BACKGROUND OF THE INVENTIONIn known impact printers one carriage is fitted with a print hammerwhile the other carriage is fitted with a rotating backing wheel havingperipheral helical ridges. The recording medium, for examplepressure-sensitive paper, is inserted between the print hammer and thewheel whereby when the print hammer strikes the paper against the ridgeson the backing wheel a dot will appear on the recording paper. If thecorresponding print hammer and backing wheel are accurately adjustedrelative to one another, characters such as letters formed by dots willbe produced when the hammer is actuated at the precise time schedule. Asthe characters are produced the carriages are moved in unisontransversely over the recording medium. In this regard it is imperativethat the carriages are rigidly connected together thereby producing thecorrect printed text material. In known printing devices thisrequirement is satisfied in that the carriages are rigidly joinedtogether by a common support. However, this known arrangement has aserious drawback in that a recording medium in the form of endless papercannot be used, but instead replaceable paper rolls must be frequentlyinserted in the apparatus.

Since there is the overriding requirement in impact printing devices ofthe present type that the carriages must be rigidly interconnected asatisfactory solution of utilizing endless paper therewith has not beenfound heretofore. Moreover, when the carriages are driven by chains,sprockets or the like, wear will soon cause misadjustment of thecarriages resulting in incorrect printmg.

The above-described drawbacks have been overcome by the presentinvention in which it is an object to provide a printing apparatushaving a pair of carriages that are immovable relative to one another,and at the same time an endless recording medium can be utilized withthe apparatus.

It is a further object of the present invention to provide drive membersconstituting endless belts, the ends of which are interconnected bycoupling elements that can be adjusted to compensate for variations inbelt lengths.

The invention will now be more fully described with reference to theaccompanying drawings:

FIG. 1 is a perspective view in diagrammatic form of a prior art impactprinting device.

FIG. 2 is a perspective view in diagrammatic form of an impact printingdevice constructed in accordance with the teachings of the presentinvention, and

FIG. 3 is a perspective view of certain details of construction of thedevice shown in FIG. 2 in which manner the drive members of the printingdevice are immovably mounted relative to each other is shown.

It should be observed that in FIGS. 2 and 3, only those parts of thedevice that are necessary for a complete understanding of the inventionhave been illustrated.

In the prior art device shown-in FIG. 1 two carriages and 11 areconnected together by a common support 12. Roll 13 of recording medium,for example pressure sensitive paper 14, has the face end thereofpassing between the carriages 10 and 1 1. Furthermore,

2 the support 12 carrying the carriages 10 and 11 can be moved forwardor backwards in a direction transverse to the direction of movement ofthe end of the paper 14 by means of drive members (not shown). Thecarriage 10 is shown provided with a print hammer 15 While the carriagel 1 has a rotatable wheel 16 having projections or cam surfaces 17. Thepaper 14 is located between the print hammer 15 and the cam surfaces 17.During the movement of the carriages over the paper 14 char- 0 acters orother indicia are printed thereon. After a line has been printed, thepaper 14 is incrementally spaced one line in a direction perpendicularto the direction of movement of the carriages l0 and 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the presentinvention as shown in FIG. 2 in which two carriages 18 and 19 are shownprovided with a print hammer 20 and a rotating socalled helical wheel 21respectively. The wheel 21 is secured to a shaft 22 and is provided withcam surfaces 23 co-acting with the print hammer 20. It will be observedthat the recording medium, for example a pressure sensitive paper 24,runs between the print hammer and the helical wheel. Print characterscan be produced on the paper in a manner explained hereinabove. A plate25 supports the carriage 18 while a corresponding plate 26 supports thecarriage 19. The aforesaid plates secure the respective carriages todrive members which in the present construction take the form of drivebelts 27 and 28. It should be apparent that it is within the scope ofthe present invention to use ropes or somewhat flexible bars instead ofthe above-described belts. The latter are shown secured to therespective plates by means of screws 29.

In accordance with the teachings of the present invention, the belts 27and 28 are immovable relative to one another and are jointly movable intheir length direction in such a manner that the carriages 18 and 19 aremoved in a direction substantially transverse to the direction ofmovement of the paper 24. As seen in FIG. 2, a guide element 30 for thepaper 24 is shown provided between the belts 27 and 28. Referring toFIG. 3, a corresponding guide element 31 is shown provided at theopposite edge of the paper. In this manner the paper 24 is movablylocated between the belts 27 and 28 and between the printing elements onthe respective carriages.

The belts 27 and 28 are shown in greater detail in FIG. 3 illustratingthe arrangement whereby the belts are immoveable relative to each other.In this connection, the belts pass over the spaced drive rollers 32 and33. The ends 34 and 35 of the belts 27 and 28 respectively areinterconnected with the other ends 39 and respectively by means of acoupling plate 36 having a link piece 37 connected to a yoke 38. Thelatter is in turn attached to the aforesaid other ends 39 and 40 of therespective belts. The manner of attachment is such that the yoke 38 maypivot slightly relative to the ends of the belts whereby differentlengths or variations in belt lengths may be compensated for when thebelts are placed around drive rollers 32 and 33. However, when theaforesaid belts are in place on the drive rollers the coupling plate 36provides for the immovable relative connection of the above-describedbelts. Because of the present construction, skidding of the belts on thedrive rollers will be of no importance, nor will wear, cooling orheating have any effect since the belts 27 3 and 28 are shortened orlengthened the same amount. Thus, the carriages 18 and 19 are accuratelyadjusted, relative to one another by the belts 27 and 28.

It is to be noted from FIG. 3 that the guides 30 and 31 are of such ashape and arrangement that the paper 24 moves between the belts 27 and28 only on that side of the drive rollers 32 and 33 at which thecarriages are located.

Other details of construction have not been shown in FIGS. 2 and 3,which are diagrammatic, since they are of known construction and form nopart of the present invention. For example, either drive rollers 32 or33 can be driven by a stepping motor. Furthermore, the paper advance atright angles to the direction of movement of the carriages can be theresult of the use of stepping motors. A plurality of guides (not shown)keep the carriages 18 and 19 at a given relative distance in a directionperpendicular to the belts 27 and 28. These guides are arranged so thatthe carriages move therealong.

What is claimed is:

1. An impact printing device comprising in combination two spacedcarriages provided with printing means, a recording medium passingbetween said spaced carriages, an elongated driving means for eachcarriage, means securing the respective driving means to each carriage,said carriages being movable in the length direction of said drivingmeans, said recording means being adapted to be moved incrementally in adirection substantially perpendicular to the direction of movement ofsaid carriages, said drive members being a pair of belts, coupling meansinterconnecting the free ends of said belts, one of said coupling meansbeing a fixed coupling member interconnecting respective free ends ofsaid belts and the other coupling means being a yoke interconnectingsecond respective free ends of said belts, and a link arm connectingsaid fixed coupling member and said yoke whereby variations in lengthsof the two belts can be compensated for.

2. An impact printing device as claimed in claim 1 further comprising apair of drive wheels for said drive belts, the latter passing over saidwheels to form two endless loops.

3. An impact printing device as claimed in claim 2 wherein saidrecording medium is a pressure-sensitive paper.

4. An impact printing device as claimed in claim 3 further comprisingedge guides located on opposite edges of said paper in order to ensurethat said paper is positioned and selectively moved between said drivebeits.

5. An impact printing device as claimed in claim 1, wherein saidprinting means constitutes a rotatable helical wheel provided with camsurfaces mounted on one carriage, a print hammer mounted on the othercarriage and adapted to co-act with said cam surfaces, the recordingmedium being arranged to be moved between said helical wheel and saidprint hammer.

1. An impact printing device comprising in combination two spacedcarriages provided with printing means, a recording medium passingbetween said spaced carriages, an elongated driving means for eachcarriage, means securing the respective driving means to each carriage,said carriages being movable in the length direction of said drivingmeans, said recording means being adapted to be moved incrementally in adirection substantially perpendicular to the direction of movement ofsaid carriages, said drive members being a pair of belts, coupling meansinterconnecting the free ends of said belts, one of said coupling meansbeing a fixed coupling member interconnecting respective free ends ofsaid belts and the other coupling means being a yoke interconnectingsecond respective free ends of said belts, and a link arm connectingsaid fixed coupling member and said yoke whereby variations in lengthsof the two belts can be compensated for.
 2. An impact printing device asclaimed in claim 1 further comprising a pair of drive wheels for saiddrive belts, the latter passing over said wheels to form two endlessloops.
 3. An impact printing device as claimed in claim 2 wherein saidrecording medium is a pressure-sensitive paper.
 4. An impact printingdevice as claimed in claim 3 further comprising edge guides located onopposite edges of said paper in order to ensure that said paper ispositioned and selectively moved between said drive belts.
 5. An impactprinting device as claimed in claim 1, wherein said printing meansconstitutes a rotatable helical wheel provided with cam surfaces mountedon one carriage, a print hammer mounted on the other carriage andadapted to co-act with said cam surfaces, the recording medium beingarranged to be moved between said helical wheel and said print hammer.